It’s not steam, but in a namesake process, oil refineries use these substances to “crack” high-molecular weight petroleum into gasoline products. These substances are “perfect” if their efficiency is limited only by diffusion. The efficiency of these substances is impeded in “poisoning.” (10[1])Leaded gasoline can impede the removal of carbon dioxide from exhaust with a “converter” named for these substances. These substances, which are called heterogeneous if they are in a different phase than reactants, provide a pathway with lower activation energy. For 10 points, name these species that increase the rate of a reaction without being consumed. ■END■